The invention relates to integrated circuits and, more specifically, to a chip that permits distributed data collection of engineering housekeeping data in a spacecraft through a serial bus, thus, significantly simplifying the spacecraft""s electrical wiring.
Today, however, spacecraft must be smaller, faster and cheaper than ever before. Smaller spacecraft can take advantage of smaller and less expensive launch vehicles. One major spacecraft component that scales with launch mass is the electronics. One large component of the electronics is the wire harness.
A necessary function in any spacecraft or instrument is collection of engineering housekeeping data to monitor health status. Such data include temperatures from distributed sensors and voltages and currents produced either directly from the various subsystems or from distributed transducers such as pressure transducers.
Traditionally, engineering data were collected from the distributed sensors with dedicated wires to a central processing unit, which multiplexed, digitized, stored, and finally transmitted the data. This centralized approach, however, requires heavy, complex electrical harness which can comprise miles of wire since each function monitored requires at least one pair of wires connected to the CPU. Reduction in core electronics including the wire harness can assist in maximizing instrument payload, save miles of wire, save on electronics and require less power and, hence, less power dissipation. Thus, there has been a need in the industry for a device that can reduce the core electronics, including the wire harness, associated with data collection.
The new approach of this invention is to use distributed data collection and to adopt a serial bus. A couple of meters of twisted pair can then replace a heavy, complex harness. Distributed processing lightens the burden on the central processing unit. New sensors can easily be added by just attaching to the bus and assigning a new address.
What is needed then is an integrated circuit that will enable the use of distributed data collection in the spacecraft by providing signal processing and an interface between the distributed sensors and the bus.
The present invention has been made in view of the above circumstances and has as an object to provide an integrated circuit that will enable the use of distributed data collection in a spacecraft. The enabling element for distributed spacecraft and instrument data collection is the remote input/output (RIO) chip of the invention enables distributed data collection in a spacecraft. The RIO chip may be an analog-digital, radiation-hardened, low-power integrated circuit. This smart data acquisition device provides all the signal processing and the interface from the distributed sensors to a standard serial Inter-Integrated Circuit (I2C) bus or a standard parallel bus.
The RIO chip measures sensory data, e.g., temperatures using external thermistors, total ionizing dose using external radFETs or PIN diodes, voltages, currents, pressures and discretes. Its sensing capability can extend to other physical quantities such as photons, vibration, etc. The RIO chip does all the necessary signal conditioning; performs the analog to digital conversion; stores data into memory; places the data as requested on a standard serial I2C or parallel bus; and provides control actions from remote processors via Digital-to-Analog Converters (DACs), and smart digital interfaces. The RIO chip is useful for remote housekeeping, high voltage converter control, stepper motor control, and spacecraft power management. It is radiation hardened and, thus, suitable for space.
One embodiment of the chip of the invention is directed to a temperature RIO (TRIO) chip for temperature measurements only. The TRIO chip measures 16 temperature channels using external platinum resistance thermistors (PRTs). It can also measure voltages only, using an external voltage reference. The TRIO chip contains all the front-end analog conditioning circuitry, the analog multiplexer (MUX), a 10-bit analog-digital converter (A/D or ADC), memory, and both a serial I2C and standard parallel interface. The TRIO chip can operate in a fixed mode, where only a particular sensor is addressed, digitized, and read out, or in a scanning mode where all 16 sensors are sequentially and continuously scanned, digitized, and stored into self-contained memory.
The chip of the invention revolutionizes spacecraft design by greatly simplifying spacecraft health data acquisition and control functions through the use of a serial bus, essentially eliminating miles of wire harness compared to traditional centralized spacecraft architecture. The unique aspect of the RIO chip is that, currently, no such chip exists for space applications. This single chip system will be a valuable enabling technology for next-generation small spacecraft.